I think it makes sense to remove this option from the default GUI. And I also think that this removal won’t noticeable change the number of users that disable JS.
- Graphical default menu (removed)
- Textual menu
about:config (still possible)
- add-ons (still possible)
I think it’s safe to assume that there are three major motiviations why to disable JS:
Users from case 1 and 3 are probably using relevant add-ons anyway (which offer a quick way to change/configure the setting) as it would be really cumbersome to go to the settings menu every time.
Users from case 2 probably won’t allow to let their users change the setting in the first place.
See also Alex Limi’s (formerly head of Firefox UX) blog post:
Checkboxes that kill your product
And one of probably many discussions about this removal: